This project builds upon a previous study which established the familiality of severe phonology disorders based upon an analysis of clinically affected status. The present study is aimed at refining the phenotype for developmental phonology disorders by examining their comorbidity and phenotypic boundaries with language disorders and reading disorders. It proposes to identify subtypes of phonology disorders and examine modes of inheritance for each subtype, while examining and allowing for gender differences which may exist in many of these disorders. In addition, developmental phonology disorders will be compared to reading disorders, or dyslexia, in terms of phenotypic similarities and patterns of inheritance. The validity of family history in predicting later learning problems will also be examined, as will the value of testing battery measurements as predictors of the outcome of therapy for individuals with preschool phonology problems. The goals here are to identify those aspects of performance during the preschool years which predict later speech and language skills, cognitive development, and academic achievement in children with preschool phonology disorders. Emphasis in all of these endeavors is focused on the analysis of quantitative measures of speech, language, and reading. As data collection of reading-disordered families and of longitudinal follow-up measures of phonology-disordered families are still in progress, analytic activity has so far focused on covariate adjustment and admixture analyses of initial phonological measures. These analyses have established the existence of effects of gender and, to a lesser extent, of socio-economic status for these measures. Despite the use of age-specific norms, age effects were noted for most of the measures considered. To some extent, this may be attributable to the lack of available population figures for adult populations, but compensatory strategies in test-taking in adulthood represent another possibility. Approaches to adjust for this phenomenon, such as standardization within developmental epoch, are currently being considered. Other efforts were directed at development and validation of a single score to reflect aspects of oral-motor and language proficiency when different, age-specific procedures must be used.